All stoves and pans are different. If you cook it on higher heat it will be done faster, lower heat it will be done slower. The lower the heat and slower the cooking the better the flavor. If you double the recipe it will take much longer. One time I made four batches in one pan and it took me about 8 hours to get them cooked! I don't suggest making more than two recipes at once. These days when I want to make two batches I usually use two pans and make the batches simultaneously.